Apple is cracking down on free iPad and iPhone games aimed at children that have left some parents facing huge credit card bills for the purchase of virtual items.

Under new rules published by the technology firm, developers making apps aimed at under-13s will need to include a "parental gate", such as a password or pin, before anything can be bought in-game.

Apple faced criticism after a flurry of high-profile cases in which children spent large amounts on virtual items within mobile games without their parents' permission.

In March, police officer Doug Crossan told reporters how his teenage son had unwittingly run up a £3,700 bill on his father's credit card on games such as Plants vs Zombies, Hungry Shark and Gun Builder. In one game he had bought a virtual chest of gold coins costing £77.98.

The UK's Office of Fair Trading is currently investigating in-app purchases within children's apps and is due to publish a report by October exploring whether such games are "misleading, commercially aggressive or otherwise unfair".

In February, Apple agreed to settle a class-action lawsuit in the US for $100m, agreeing to refund parents in cash or credits for its iTunes Store. The US lawsuit was launched after concerns raised by the parents of a nine-year-old girl from Pennsylvania who bought $200 (£132) of virtual money from three free games.

The new rules are also aimed at protecting children from inappropriate advertising and data collection within iPhone and iPad apps.

"Apps primarily intended for use by kids under 13 must get parental permission or use a parental gate before allowing the user to link out of the app or engage in commerce," the new guidelines explain.

They also bar developers from including "behavioural advertising", where ads are shown based on tracking what a child has been doing within an app, and state that any app aimed at children under 13 must include a privacy policy.

The changes are tied to the upcoming launch of a dedicated "Kids" app category on the company's App Store. Apple is hiring an editorial team to curate the new section and provide recommendations for parents, and wants children's app developers to clearly understand the criteria for being selected.

The new rules have grey areas. Some of the App Store's most lucrative games – such as The Simpsons: Tapped Out, Clash of Clans and Candy Crush Saga – are aimed at all ages rather than just children, so will not be covered by the new rules.

Developers are hoping the combination of tighter rules and better promotion on the App Store will boost business at a time, according to Ofcom, when 91% of British parents who own tablets say their children either use the devices or have their own.

"I think that it is positive that app developers who haven't been behaving ethically are being forced to do so," said Kate Wilson managing director of British app and book publisher Nosy Crow.

"It's what's right for children, it's reassuring for parents and it's good for those of us who aren't doing the sleazy stuff to have the whole market clean and credible."